Partial ligature support (Emacs 24.4.3, 24.5.1, Windows (unable to work under Ubuntu))

With the Wiki support using composition-function-table, I have some ligature support under Windows, but not all (for example, ++ == !== ===, <| <|>, and the like, but frustratingly not more Clojure-useful ones like -> ->> etc). The regexes should have matched the appropriate ligatures, but maybe font-shape-gstring wasn't giving a proper result? This is a bit of emacs wizardry that puzzles me, but I tested the regexes for the arrows (the (45. line) and I feel like it should have worked. So I can't tell if this is a platform, Emacs, or FiraCode issue.

Attached is a clip showing the results of the ligatures from the FiraCode front page to show which are getting results and which aren't. This was under Windows 7 and emacs 24.4.3 and 24.5.1; I attempted it under 24.4.3 using Ubuntu under VirtualBox and no ligatures worked (not certain why).

Start by reproducing the reported behavior with Emacs 24.4.3 or 24.5.1, Fira Code, and the attached ligature examples on Windows and Ubuntu. Inspect the composition-function-table regexes, including the arrow patterns, and check whether font-shape-gstring produces results; done means the missing ligatures render consistently or the platform, Emacs, or font limitation is identified.